Skimming weir

ABSTRACT

A broad crested weir with a converging trapezoidal entrance region, for maximizing velocity of surface flow relative to flow at submerged levels in the adjacent fluid reservoir. The weir&#39;&#39;s lateral walls are generally vertical in their upper rear sections and are laterally spaced a given distance apart. The lower forward sections of the walls converge from a greater laterally spaced apart distance along the forward edge of the weir crest to the given lateral distance near the weir exit, whereby entering fluid velocity at the level of the weir crest is reduced relative to fluid velocities above the weir crest.

United States Patent [72] Inventor Edward F. Gillette Greenwich, Conn. (737 Canal St., Bldg. 16,

Stamford, Conn. 06902) [21] Appl. No. 883,071

[22] Filed Dec. 8, 1969 [45] Patented Mar. 2, 1971 Continuation-impart of application Ser. No. 718,467, Apr. 3, 1968, now abandoned.

[54] SKIMMING WEIR 5 Claims, 11 Drawing Figs.

[52] U.S. Cl 210/169, 210/540 [51] Int. Cl B01d 21/24 [50] Field ofSearch 210/167, 169, 532, 540

[5 6] References Cited UNITED STATES PATENTS 2,701,235 2/1955 King 210/(1 69UX) Primary Examiner-John Adee Attorney-Mattern, Ware & Davis ABSTRACT: A broad crested weir with a converging trapezoidal entrance region, for maximizing velocity of surface flow relative to flow at submerged levels in the adjacent fluid reservoir. The weirs lateral walls are generally vertical in their upper rear sections and are laterally spaced a given distance apart. The lower forward sections of the walls converge from a greater laterally spaced apart distance along the forward edge of the weir crest to the given lateral distance near the weir exit, whereby entering fluid velocity at the level of the weir crest is reduced relative to fluid velocities above the weir crest.

SKIMMING WEIR.

RELATED APPLICATION This application is a continuation-in-part of my copending parent application entitled Skimming Weir, Ser. No. 7 18,467, filed Apr. 3, 1968 now abandoned.

BACKGROUND OF THE INVENTION This invention relates to weirs for skimming or. preferentially removing the topmost layers of fluid flowing therethrough. More particularly, it relates to a weir having no moving parts, and wherein the desired operation is achieved by selection of contours of the lateral walls defining the lower entranceto the weir. The invention has particular utility in applications such as swimming pools or other fluid reservoirs wherein it is desired to remove floating or partially submerged debris entrained in a minimum amount of water. For convenience of disclosure, the invention is disclosed in the specific environment of a swimming pool weir.

Known swimming pool weirs for removing the upper layer of water are typified by those described in U.S. Pat. No. 2,701,235 to King, and U.S. Pat. No. 2,826,307 to Pace. King teaches a pivoted gate positioned by a buoyant float restingon the water in a weir pocket. The pivoted gate restricts fluid flow at lower levels while the float adjusts the gate for varying mean water levels. Such construction suffers various disadvantages causedby the presence of moving parts. Turbulent water may render the weir inoperative. The moving parts can be jambed by debris and can suffer accidental damage caused by swimmers.

Pace contemplates a weir with an articulated ramplike crest. Paceshows this weir recessed from the fluid reservoir. The recess is formed with generally vertical sidewalls converging to a laterally spaced apart distance approximately equal to the lateral dimension of the weir crest.

The weir crest is comprised of a buoyant float mounted on a leaf spring for articulation at an angle rearward withrespect to vertical. The buoyant weir crest pivots in response to the water level on either of its sides to adjust the amount of water to be taken in. The weir does not achieve the overflowing removal of leaves and other debris entrained in surface water, as it automatically adjusts to remove only a thin layer of water at a time. This thin layer skimming effect tends to screen the debris from overflowing water and leave the debris in the pool, which is highly undesirable.

These and other disadvantages of prior art constructions are avoided according to the present invention by contouring the forward lateral walls of the weir to increase the velocity of the surface layers of water entering the weir relative to the velocity of the lower layers in that same vicinity, thereby efficiently removing surface debris. This is accomplished with no moving parts, and the resulting weir is inexpensive and reliable as compared to prior art devices.

Accordingly, a primary object of the invention is to provide a novel skimming weir having no moving parts.

A further object of the invention is toprovide a weirof the above character in which the desired fluid flow configuration is achieved by contouring the lateral walls defining the weir fluid passageway.

Yet another object of the invention is to provide a weir of the above character wherein fluid flow near the surface of the water entering the weir fluid passageway is greater than the velocity of the fluid flow near the bottom of the entrance thereto.

A still further object of the invention is to provide a weir of the above character wherein the weir may be formed as in integral cast or moldedunit, affording :economies in production and reliability of operation.

Other and more specific objects will be apparent from the features, elements, combinations and operating procedure disclosed in the following detailed description and shown in the drawings.

THE DRAWINGS FIG. 1 is a schematic perspective view of a swimming pool incorporating a weir according to the invention;

FIG. 2 is a top plan view ofthe weir shown in FIG. 1;

FIG. 3 is a sectionalview taken along line 3-3 of FIG. 2, showing a fluid flowing through the weir;

FIG. 4 is a front elevation view of the FIG. 2 weir;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 3;

FIG. 6 is a perspective view, partially broken away, of the weir mounted in a swimming pool wall;

FIG. 7 is a perspective diagrammatic view of the weir and water flowing therethrough;

FIG. 8 is a sectional view taken along the plane 8-8 of FIG.

. 3, showing fluid flowing through the weir near the entrance region thereof;

FIG. 9 is a sectional view taken along the plane 9-9 of FIG. 3, showing fluid flowing through the weir;

FIG. 10 is a sectional-view taken along the plane 10-10 of FIG. 3, showing fluid flowing through the weir; and,

FIG. 11 is a cross section taken along the plane ll-I1 of FIG. 3, showing fluid flowing through the weir near the exit end thereof.

Referring to FIG. 1, weir assembly 20 is installed in the wall 22of a liquid reservoir illustrated as a swimming pool with the liquid level indicated at 24. The same weir assembly 20 is also shown in FIG. 7. Assembly 20 includes a generally horizontal passage 26 for conducting water from the pool to sump 28 beneath removable access cover 29 (FIG. 3). A removable screen basket 30 can be positioned in sump 28 at a point lower than the bottom of passageway 26, to screen out large objects such as leaves. Water in the bottom of sump 28 is removed through pipe 32 by means of a pump (not shown), and may be filtered before being returned into the pool. Details of the sump construction, as such, are not part of the present inventron.

' Passage 26 is defined by lateral walls 34 extending from the intake or forward end 35 rearwardly to the exit orifice end 36. Each lateral wall 34 includes an upper rear section 37 and a lower forward section 38, the sections 37 and 38 of each wall 34 merging into one another in laterally aligned transitionregions 40 extending diagonally downward from near the upper forward end of passageway 26 to the vicinity of the lower edge of orifice 36.

Upper rear sections 37 are substantially vertical and parallel to each other. They have a generally triangular surface shape, extending substantially the full length of passage 26 near the top thereof, and tapering to a point near the bottom rearward edge of passage 26. The sections 37 of walls 34 are spaced apart a given distance, and define at their rear edges the sides of exit orifice 36.

Lower forward sections 38 of passage walls 34 extend from transition lines 40 to respective points 42 at the bottom entrance edge of passageway 26, points 42 being equally spaced from a central axis of passageway 26 a distance greater than the given distance separating parallel facing sections 37 of the walls 34. In the embodiment illustrated,.sections 38 are planar and lie on adjacent faces of an imaginary pyramid having its base on the horizontal bottom surface 44 of passageway 26 and its apex 45 near the upper forward region of passageway 26, with the imaginary edge 46 on which the faces intersect inclining downwardly and rearwardly along the center of the passageway toward the bottom edge of orifice 36. The imaginary edge 46 is shown in FIG. 3 and FIG. 4. The horizontal bottom surface 44 of the pyramid is the broad crested weir of the weir assembly 20.

The weir is positioned in the wall of swimming pool 22 so that the normal water lever 24 is presented to the intake or forward end 35 of passage 26 near the top thereof, with the wider lower entrance region submerged. The parallel sections 37 of walls 34 extend upward from this entrance region in the manner of a notch, as is shown in the embodiment illustrated, in order to assure that the surface of the water is always presented to the opening and not to the wall above the opening. This extension increases the range of mean water levels from which the weir may receive and skim the surface layer of liquid wherein waste and debris normally reside.

When so positioned in a swimming pool wall, water flows from the pool through the passage 26 and into the sump basket filter 30, where leaves or other large debris entrained in the water are separated therefrom.

The contours of walls 34 can be described by examining the shape of the water flow through passage 26, because the water closely conforms to the walls of the passageway. FIGS. 8, 9, 10, and 11 are successive sectional views of the water flowing through passage 26, said sectional views being taken along the lines indicated in FIG. 3. The sectional view of FIG. 8, taken across the entrance to passageway 26, shows fluid flow in the shape of a trapezoid 80. The base 82 of the trapezoid 80 ex tends between points 42 and coincides with the bottom surface 44 of passage 26. The sides 84 of trapezoid 80 coincide with the water-contacted sections 38 of walls 34. The top 86 of trapezoid 80 is formed by the free surface of the flowing water.

FIG. 9 is a successive sectional view of the water flowing through passage 26, taken further inward along the passageway 26, as indicated in FIG. 3. The bottom 92 of the trapezoid 90 also lies along bottom surface 44, but has less lateral width than the bottom 82 of trapezoid 80. The inclined sides 94 of trapezoid 90 coincide with the water-contacted sections 38 of walls 34. Above point 95 corresponding to transition lines 40 of walls 34, the fluid flow is shaped by parallel facing sections 37 of the walls 34. In FIG. 9 the trapezoid 90 is formed by connecting the two points 95, and the portion of the flow above the trapezoid 90 is in the form of a rectangle 98. It will be noted that the water surface 96 extends across the same lateral width as does the water surface 86 of FIG. 8, while the height and base width of the trapezoid 90 have become significantly smaller than those of trapezoid 80.

The cross section of FIG. is taken further inward along the passage 26, as indicated in FIG. 3. The base 102 of the trapezoid 100 lies along the bottom surface 44 of the channel. The sidewalls 102 of the trapezoid are again located where the water contacts inclined sections 38 of walls 34, and the top of the trapezoid is formed by connecting points 105 corresponding to points on transition line 40. In FIG. 10 the greater volume of the flow through the passage occurs between the vertical parallel facing sections 37 of walls 34, which coincide with the sides 107 of a rectangle 108 positioned directly above trapezoid 100. The water surface 106 again has the same lateral width as in FIGS. 8 and 9; however, it is at a somewhat lower vertical height above the bottom surface 44. This drop in height of water surface also appears in FIG. 3, and is a result of the phenomenon of flow at critical depth, as will be described below. FIG. 11 is the cross section of the water flow taken at the exit orifice end 36 of passageway 26, as indicated in FIG. 3. At this position the flow is shaped entirely by the bottom surface 44 and the vertical upstanding sections 37 of walls 34, shaping the fluid flows into a rectangular stream illustrated by rectangle 110. The top of the fluid 116 extends across the same lateral width as in FIGS. 8, 9, and 10, and it is found at a lower vertical height above bottom surface 44.

The above description indicates that the passageway 26 defined by the walls 34 and bottom surface 44 is comprised of a converging or diminishing trapezoidal entrance region formed by sections 38 of the walls 34, and a rectangular region always formed above the converging trapezoid and between the vertical parallel facing sections 37 of walls 34. The passageway 26 having that configuration induces a fluid flow pattern which preferentially removes the leaves and other surface debris from the surface of the swimming pool. This effect is achieved because surface water flowing through passage 26 is not impeded in any manner. However, water entering the passage 26 and flowing near the bottom surface 44 thereof is retarded or restricted in its passage by the converging trapezoidal entrance region. It is the restriction of flow near bottom surface 44 which produces a subsurface fluid flow retarded with respect to the surface flow at the forward or entrance end 35 of the passage. Conversely, the flow velocity of surface fluid entering the passage is greater than the flow velocity at subsurface levels.

The higher relative velocity of the surface flow may be understood by reference to FIG. 7. Water levels flowing nonturbulently through a passage may be described as exhibiting laminar flow characteristics. That is, the principal component of a velocity vector of any given increment of water in the flow is in the direction of the flow. Therefore, an increment of water which enters passage 26 at a' given height above the bottom thereof tends to remain at that height as it flows through the passage. The flow of water illustrated in FIGS. 3, 8, 9, l0, and 11 is cut away in FIG. 7 except for increments 52, 54, 56, and 58. The two increments 52 and 54 entering the passageway 26 have equal volume and an equal vertical dimension h. The horizontal or lateral dimensions correspond to the width dimensions of the passageway 26 at its entrance, and thus the lower increment 54 is laterally wider than upper increment 52. Because each increment contains the same volume, the length or axial dimension of increment 54 is very much smaller than that of increment 52. These axial dimensions are proportional to the velocity of each increment as it enters passage 26. The two exiting increments 56 and 58 also have the same volume and vertical dimension h as the increments 52 and 54. Upper increments 52 and 58 may be considered as a part of the same layer of water flowing through the passage 26. This is an approximation, as the surface height above bottom surface 44 is less at the exit orifice 36 than at the entrance end 35 of the passage 26, due to the phenomenon of critical depth as illustrated in FIG. 3 and described herein. The lateral width of passage 26 is the same throughout the layer of flow containing upper increments 52 and 58, and therefore the velocity of the surface water flowing through the passage is not restricted. Thus entering increment 58 has the same axial dimensions as does exiting increment 52, indicating substantially the same velocity of surface flow at each end of passage 26.

Lower increments 54 and 56 are also equal volumes of a layer of flow near the bottom of passage 26. The lateral width of this layer becomes smaller as the length of the channel is traversed. The axial dimension of the increment is therefore increased, delivering to the exiting increment 56 a volume equal to that of the entering increment 54, which has a relatively small axial dimension corresponding to a low entering velocity and relatively large lateral entrance width. This lower increment of water flowing through passage 26 is shaped by the contours of the walls 34 of passage 26 into an exiting lower increment 56 with an increased axial dimension corresponding to a greater exiting velocity. Such greater velocity is equal to that of increment 58 taken from the upper, straightthrough, layer of flow.

The flow through the passage is made up of a progression of increments such as 52 and 54. The greater axial length of increment 52 relative to that of increment 54 at the entrance 35 to the passage 26 results in a surface water flow at greater velocity near the entrance than the velocity of water flow at subsurface levels near the entrance. Therefore, the surface water entraining leaves and other debris flows from the pool at a greater velocity than subsurface water, achieving the preferential removal of the surface wastes and debris.

Water flowing through the weir assembly displays the hydraulic phenomenon of flow at critical depth. This phenomenon occurs in fluid flow over a broad crested weir and in fluid flow through a constricted channel, both of which features are incorporated in the weir assembly 20. Bottom surface 44 is a broad crested weir, and the forwardly inclined sections 38 of walls 34 constrict passage 26. Critical depth is defined in Hydraulics, Third Edition, by King and Wisler (1933 Wiley) as the depth of fluid flow above a weir crest or channel bottom at which the maximum volume discharge of fluid occurs for a given total energy gradient of the fluid just prior to entering the weir of constricted channel. The total energy gradient referred to comprises the potential, kinetic, and pressure energies present in a fluid, and, is often referred to as the head. Thus, for any given head of water in swimming pool 22, the weir assembly automatically induces flowat the critical depth for that given head, achieving the greatest volume discharge of water from the pool for that given depth. This feature assures rapid and effective skimming of the water in the pool.

it should be noted that the desirable features of the weir assembly 20 may be achieved by assemblies having somewhat different configurations than the embodiment described above and which are also a part of this invention. For instance, the walls 34 do not require a sharp transition line 40 between the sections 37 and 38. Such transition could be rounded, thereby creating convexiy curved walls. It is believed essential that the entrance to the passage be laterally wider at its bottom than at its top, and that some constriction be introduced into the passage near the bottom thereof.

The weir can be conveniently molded integrally with the sump, and can be permanently installed in the wall of the reservoir if desired. Suitable materials of construction include moldable artificial resins, concrete, metals, or the like.

The weir as above described affords a number of advantages as compared to the prior art. The desired flow patterns are achieved by contouring the lateralwalls defining the fluid passageway. Since this eliminates moving parts, the cost of producing and maintaining the weir is reduced, while substantially greater reliability in operation is achieved. The weir effectively removes partially submerged as well as floating debris, which cannot be achieved with weirs of the floating gate type.

Since the foregoing description and drawings are merely illustrative, the scope of the invention has been broadly stated herein and it should be liberally interpreted to secure the benefit of all equivalents to which the invention is fairly entitied.

lclaim:

l. A skimming weir for mounting in a sidewall of a fluid reservoir at the mean fluid level, said weir comprising:

A. opposed walls defining a horizontally elongated passageway for conveying upper levels of said fluid to a sum B. said passageway being vertically elongated sufficiently to span a range of fluid levels; a

C. said passageway being provided with an entrance having its greatest horizontal width near the bottom thereof; and

D. said greatest horizontal width converging to a lesser horizontal width within said passageway.

2. A skimming weir, comprising:

A. first and second lateral walls defining a horizontally elongated fluid passageway extending from a forward intake end rearwardly to a vertically elongated rear discharge orifice;

B. upper rear portions of said walls being substantially parallel and defining at their rear edges the sides of said discharge orifice; and

C. lower forward portions of said walls converging inwardly, upwardly and rearwardly to join said respective portions in transition regions extending rearwardly and downwardly toward the bottom of'said orifice.

3. A skimming weir, comprising:

A. first and second lateral walls defining a horizontally elongated passageway extending along an axis from an intake end rearwardly to a vertically elongated discharge orifice;

B. each of said lateral walls including a substantially vertical upper rear portion connected along its length to a lower forward portion;

C. said upper portions being laterally spaced from said axis a given distance; and

D. said lower portions being spaced apart from said axis a distance greater than said given distance at the intake end of said passageway and converging to said given distance near said discharge orifice.

4. A skimming weir com risin i A. first and second iatera walls defining a horizontally elongated passageway extending along an axis from an intake end rearwardly to a vertically elongated discharge orifice;

B. each of said lateral walls including a substantially vertical upper rear portion and a lower forward portion;

C. said upper rear portions being substantially parallel and spaced apart a given distance from one another and defining at their rear edges the sides of said discharge orifice;

D. said lower forward portions of said walls lying on adjacent faces of an imaginary pyramid having its horizontal base at the bottom of said passageway, its apex near the upper forward portion of said passage, and an edge in which said faces intersect, said edge inclining downwardly and rearwardly from said apex toward the bottom of said orifice; and

E. each said lower forward portion joining its corresponding upper rear portion in a transition region parallel to said edge.

5. A skimming weir, comprising:

A. first and second lateral walls defining a horizontally elongated passageway extending along an axis from an intake end rearwardly to a vertically elongated discharge orifice;

B. each of said lateral walls including a substantially vertical upper rear portion and a lower forward portion;

C. said upper rear portions being substantially parallel and spaced apart a given distance from one another and defining at their rear edges the sides of said discharge orifice; and

D. said lower portions converging inwardly toward said upper rear portions from a distance greater than said given distance at the bottom front edge of said passageway, to merge into their respective upper rear portions in opposed regions extending diagonally downwardly and rearwardly from near the upper forward end of said passageway to the vicinity of the lower edge of said orifice. 

1. A skimming weir for mounting in a sidewall of a fluid reservoir at the meAn fluid level, said weir comprising: A. opposed walls defining a horizontally elongated passageway for conveying upper levels of said fluid to a sump; B. said passageway being vertically elongated sufficiently to span a range of fluid levels; C. said passageway being provided with an entrance having its greatest horizontal width near the bottom thereof; and D. said greatest horizontal width converging to a lesser horizontal width within said passageway.
 2. A skimming weir, comprising: A. first and second lateral walls defining a horizontally elongated fluid passageway extending from a forward intake end rearwardly to a vertically elongated rear discharge orifice; B. upper rear portions of said walls being substantially parallel and defining at their rear edges the sides of said discharge orifice; and C. lower forward portions of said walls converging inwardly, upwardly and rearwardly to join said respective portions in transition regions extending rearwardly and downwardly toward the bottom of said orifice.
 3. A skimming weir, comprising: A. first and second lateral walls defining a horizontally elongated passageway extending along an axis from an intake end rearwardly to a vertically elongated discharge orifice; B. each of said lateral walls including a substantially vertical upper rear portion connected along its length to a lower forward portion; C. said upper portions being laterally spaced from said axis a given distance; and D. said lower portions being spaced apart from said axis a distance greater than said given distance at the intake end of said passageway and converging to said given distance near said discharge orifice.
 4. A skimming weir, comprising: A. first and second lateral walls defining a horizontally elongated passageway extending along an axis from an intake end rearwardly to a vertically elongated discharge orifice; B. each of said lateral walls including a substantially vertical upper rear portion and a lower forward portion; C. said upper rear portions being substantially parallel and spaced apart a given distance from one another and defining at their rear edges the sides of said discharge orifice; D. said lower forward portions of said walls lying on adjacent faces of an imaginary pyramid having its horizontal base at the bottom of said passageway, its apex near the upper forward portion of said passage, and an edge in which said faces intersect, said edge inclining downwardly and rearwardly from said apex toward the bottom of said orifice; and E. each said lower forward portion joining its corresponding upper rear portion in a transition region parallel to said edge.
 5. A skimming weir, comprising: A. first and second lateral walls defining a horizontally elongated passageway extending along an axis from an intake end rearwardly to a vertically elongated discharge orifice; B. each of said lateral walls including a substantially vertical upper rear portion and a lower forward portion; C. said upper rear portions being substantially parallel and spaced apart a given distance from one another and defining at their rear edges the sides of said discharge orifice; and D. said lower portions converging inwardly toward said upper rear portions from a distance greater than said given distance at the bottom front edge of said passageway, to merge into their respective upper rear portions in opposed regions extending diagonally downwardly and rearwardly from near the upper forward end of said passageway to the vicinity of the lower edge of said orifice. 